I heat my tiny shop with a little barn/bathroom electric heater. One in mild weather and two if its really cold. The problem is that the thermostats are terrible. Turn them up slightly and the shop goes to about 75 degrees. Down slightly and we are at 45 degrees.
So I bought a thermostat and mounted it in a double gang box along with an outlet. Wired it so that the thermostat controls the outlet and plugged in the heater. Left the heater in the ON position so that the thermostat would control it. In really mild weather it does fine. When its colder, not so much. Turns out the outlet and plug get warm when there is a prolonged draw. The warmth fools the stat and turns it off. With both heaters plugged in, its even worse. Didn't see that coming. Got to rewire it and separate the stat from the plug in separate boxes.